Apparatus and method for fracturing a hard material

ABSTRACT

Apparatus  10  for fracturing a hard material  24  includes a loading head  12  provided with a guide tube  14  for receiving a cartridge  16  containing a charge of energetic material. A flexible elongated conduit  26  is advanced and retracted through the tube  14  via a reel  88.  The conduit  26  is also in communication with a stemming loader  30  which holds a supply of particulate stemming material. Tube  14  is supported by a carriage  70  which is able to slide along a member  52  by operation of a rod  76  and cylinder  78.  A motor  60  is also coupled to the member  52  to effect rotation of the member  52  and thus tube  14  about an axis A which is parallel to a hole  18  drilled in the material  24.  By appropriate operation of the motor  60  and rod  76,  the tube  14  can be moved into and out of alignment with the hole  18.  When the tube  14  is moved into alignment with the hole  18,  cartridge  16  is loaded into the tube  14  and pushed through the tube  14  into the hole  18  by advancing the conduit  26.  Particulate stemming material from the loader  30  is then injected through the conduit  26  into the hole  18.  Tube  14  and conduit  26  are then retracted from the hole  18  and subsequently moved out of alignment therewith. The cartridge  16  may then be initiated to cause fracturing of the material  24.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefits under 35 U.S.C. §119of U.S. Provisional Patent Application Serial No. 60/359,251, of thesame title, filed Feb. 20, 2002, to Carnegie-Smith, which isincorporated herein by this reference in its entirety.

FIELD OF THE INVENTION

[0002] This specification relates to an apparatus and method forfracturing a hard material particularly, thought not exclusively, forapplication in mining and civil excavation.

BACKGROUND OF THE INVENTION

[0003] The most common underground mining rock fracturing and/orbreakage processes are:

[0004] (a) mechanical methods using rock cutting techniques usingspecialised equipment such as tunnel boring machines (TBM's) and impactbreakers; or

[0005] (b) drill and blast techniques where holes are drilled into arock face, explosive charges placed in the drillholes connected up to afiring box, and once the area is clear the explosives initiated. Theinitiated explosives create shock waves and a rapid build up of gaspressure to cause the rock to crush, fracture and disintegrate intosmaller pieces.

[0006] A major impediment with the drill and blast technique or indeedother techniques using explosives is its cyclical nature. The techniqueis slow and tedious because a miner operating a drilling machine muststop drilling, get down from the machine and manually load theexplosive. This means that either additional personnel or equipment isrequired to charge and load the explosives and initiators or productivecycle time is lost while the drill operator stops to load the drillholes as well.

[0007] Recently in mining and civil excavation work, small chargeblasting or controlled fracture techniques have been introduced as analternative to conventional drill-and-blast, mechanical breakers,chemical expansion agents and, in some cases, hand methods. The term“small charge blasting” as used herein includes any excavation methodwhere relatively small amounts of an energetic substance (typically akilogram or less) is consumed for each drill hole or alternatively wherea fluid is sealed in the bottom of a drill hole and pressurised in orderto propagate a fracture in the material to be broken. The term “sealing”refers to the partial or total blockage of the hole to impede escape ofthe high-pressure gas pulse or fluid from the hole. Examples of smallcharge blasting devices and methods are described in U.S. Pat. Nos.5,765,923, 5,308,149 and 5,098,163.

[0008] The pressurised fluid can be generated in a number of differentways including by: combustion of a propellant; an electrical dischargeinto a conductive fluid; or mechanical compression of the fluid. Someform of stemming seals the hole for sufficient time to enable the fluidpressure to cause fracturing of the rock.

[0009] Small charge breakage can be highly mechanised and automated sothat it can be carried out more or less continuously to increaseproductivity. It can also allow excavation machinery to remain near theface due to reduced flyrock discharge, and has an additional advantageof producing a relatively small seismic signature due to the smallamount of blasting agent used and the lack of a shock wave.

[0010] By and large, the systems used for automated small chargebreakage have relied on either gas injectors for injecting a compressedgas pulse into a hole where a barrel of the gas injector itself acts asa stemming bar or alternately have coupled a cartridge containingenergetic material directly to an end of a stemming bar which is theninserted into a hole. One problem with such systems is damage to thecomponents inserted into the drill hole due to the energy released andpressure waves produced. Additionally, it is difficult to accurately andquickly align the gas injector or stemming bar with the drilled hole. Itis typical in such system for a common boom to support both the drillingsystem, (eg a rail, drill steel and drifter), and a gas injector or astemming bar. However the additional weight provided by the stemming baror gas injector upsets the weight distribution of the boom and makes itdifficult to maintain accurate alignment. This is exacerbated by theaddition of a recoil mechanism which is often incorporated to reducerecoil forces on the system arising from the injector/stemming bar beingheld in the hole when the energetic substance is initiated.

SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to provide an apparatusand method for fracturing of hard material which attempts to alleviatethe disadvantages in the above described prior art.

[0012] According to the present invention there is provided an apparatusfor fracturing a hard material, said apparatus including at least:

[0013] a loading head provided with a guide for receiving a cartridgecontaining a charge of energetic material, and guiding said cartridgeinto a hole formed in a face of a hard material to be fractured;

[0014] a system for advancing said cartridge along said guide to a toeof said hole; and,

[0015] a stemming loader for loading a particulate stemming materialinto said hole through said guide.

[0016] Preferably said system for advancing said cartridge includes aflexible elongated member having a first end which abuts an end of saidcartridge distant said hole, and a device for advancing and retractingsaid flexible elongated member.

[0017] Preferably said flexible elongated member is a conduit andconstitutes a part of said stemming loader, said stemming loader furtherincluding a stemming injector for injecting particulate stemmingmaterial into a second end of said conduit.

[0018] Preferably said stemming injector includes a blower for blowingsaid particulate stemming material into and along said conduit.

[0019] Preferably said apparatus further includes an alignment mechanismfor moving said guide into and out of alignment with said hole.

[0020] In one embodiment, said alignment mechanism rotates said loadinghead about an axis parallel to an axis of said hole, to move the guideinto and out of alignment with said hole.

[0021] However, in an alternate embodiment, said mechanism slides saidloading head along an axis perpendicular to an axis of said hole, tomove the guide into and out of alignment with said hole.

[0022] Preferably said apparatus further includes a drilling system fordrilling said hole, said drilling system including a rail and a drillslidably mounted on said rail, wherein said alignment mechanism issupported on said rail.

[0023] It is further envisaged that said loading head includes astemming bar which can be moved into and out of alignment of said holefor insertion into said hole to support said particulate stemming.

[0024] Preferably said stemming bar includes a transmitter fortransmitting a signal into said hole for operating an initiator or adetonator contained in said cartridge.

[0025] According to the present invention there is also provided amethod of fracturing a hard material, said method including the stepsof:

[0026] providing a guide for receiving a cartridge containing a chargeof energetic material;

[0027] aligning said guide with a hole formed in a face of a hardmaterial;

[0028] inserting the cartridge into said guide;

[0029] advancing said cartridge along said guide into said hole;

[0030] injecting particulate stemming material through said guide intosaid hole; and,

[0031] initiating said energetic material.

[0032] Preferably said method of aligning includes advancing said guideinto abutment with said face of said hard material.

[0033] Preferably said step of advancing said cartridge includes pushingsaid cartridge along said guide.

[0034] Preferably said step of pushing includes advancing a length of aflexible elongated member into said guide to push said cartridge alongsaid guide into said hole.

[0035] Preferably said step of injecting particulate material includesforming said flexible elongated member as a conduit and blowing saidparticulate stemming material through said conduit into said hole.

[0036] Preferably said method further includes a step of retracting saidconduit from said hole as said particulate material is blown into saidhole.

[0037] Preferably said method further includes a step of attaching saidguide to a drilling system which includes a rail and a drill mounted onsaid rail and supporting said guide on said rail.

[0038] Preferably said method includes providing an alignment mechanismfor moving said guide into and out of alignment with said hole.

[0039] Preferably said method further includes a step of providing astemming bar coupled to said alignment mechanism, moving said guide outof alignment with said hole; and moving said stemming bar into alignmentwith said hole and into abutment with said particulate stemming in saidhole.

DESCRIPTION OF FIGURES

[0040] An embodiment of the present invention will now be described byway of example only with reference to the accompanying drawings inwhich:

[0041]FIG. 1 is an exploded view of a loading head incorporated into theapparatus for small charge blasting;

[0042]FIG. 2a is an elevation view of an apparatus for small chargeblasting mounted on a conventional drillrig;

[0043]FIG. 2b is a plan view of the apparatus depicted in FIG. 2a; and,

[0044] FIGS. 3-11 depicted in sequence a method of small charge blastingusing the apparatus depicted in FIGS. 1-2 b.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0045] Referring to the accompanying drawings and in particular, FIGS.1-3, 6 and 7 an apparatus 10 for small charge blasting includes aloading head 12 provided with a guide in the form of a tube 14 forreceiving a cartridge 16 containing a charge of energetic material, andguiding the cartridge 16 to a collar 18 of the hole 20 formed in a face22 of a hard material such as a body of rock 24 to be fractured. Theterm “energetic material” is used here in a general sense to include apropellant, an explosive, a pyrotechnic, and any combination thereof.The apparatus 10 also incorporates a flexible elongated member in theform of a conduit 26 as part of a system for advancing the cartridge 16along (and more particularly through) the tube 14 to a toe 28 of thehole 20. A stemming loader 30 (see FIG. 7) is also provided for loadinga particulate stemming material, such as sized and graded aggregatematerial, into the hole 20 through the tube 14.

[0046] As shown in FIGS. 2a and 2 b, an embodiment of the apparatus 10is attached to a boom 32 of a jumbo 34 and also supports a drillingsystem or rig 36 comprising a rail 38, drifter 40 and drilling steel 42,all of conventional construction.

[0047] Looking at the components of the apparatus 10 in more detail withparticular reference to FIG. 1, the loading head 12 includes a swing arm44 comprising a first relatively short member 46 which is attached atone end 48 to one end 50 of a second longer member 52 which extendsperpendicular to the member 46. An opposite end 54 of the member 46 isformed with a profiled socket 56 for receiving a splined drive shaft 58of a motor 60.

[0048] The motor 60 is attached by a series of bolts 62 to a motorbracket 64. The motor bracket 64 in turn is coupled by bolts 66 to amounting bracket 68. The mounting bracket 68 is attached to the rail 38of the drilling system 36.

[0049] A carriage 70 is slidably mounted on the member 52. To facilitatethe sliding motion of the carriage 70, the carriage incorporates anumber of rollers or wheels 72. The carriage 70 supports a cradle 74 towhich is attached the tube 14.

[0050] A rod 76 of an extension cylinder 78 is attached to a bracket 80of the carriage 70. End 82 of the cylinder 78 opposite the rod 76 iscoupled by a bracket 84 to an end 86 of the member 52.

[0051] The motor 60 moves the tube 14 by way of rotation about an axis Aparallel to an axis B of the hole 18 (see FIG. 5) into and out ofalignment with the hole 18. Further, the extension cylinder 78 can beoperated to move the carriage 70 along the member 52 and thus lineallyadvance and retract the tube 14 from the face 22. The combination of themotor 60, swing arm 44, rod 76, extension cylinder 78 and carriage 70constitute an alignment mechanism for moving the tube 14 into and out ofalignment with the hole 18.

[0052] Referring to FIG. 7, it can be seen that the conduit 26 which isused for advancing or pushing the cartridge 16 is wound on a reel 88which can be operated to advance or pay out the conduit 26 (i.e. feed itinto and along the tube 14) and to retract or reel it in. When the reel88 pays out the conduit 26, one end of the conduit 26 pushes thecartridge 16 through the tube 14 towards and into the hole 20. However,the tube 26 also forms part of the stemming loader 30 used for loadingparticulate stemming material into the hole 20. In this regard, a secondend of the tube 26 can be selectively placed into fluid communicationwith a stemming feed pipe 90 into which is fed particulate stemmingmaterial from a stemming kettle 92. An end of the stemming feed pipe 90upstream of the kettle 92 is coupled to a blower 94. The blower 94 blowsair into the stemming feed pipe 90 in which is entrained the particulatestemming material from the kettle 92. Thus, the blower 94 blows theparticulate stemming material through the conduit 26 and the tube 14into the hole 20.

[0053] As also shown in FIG. 7, an upstream end 96 of the tube 14 isprovided with a breach 98 for facilitating loading of cartridges 16 intothe tube 14. The breach 98 is held by a breach support 100. In thisparticular embodiment, the cartridge 16 is pre-coupled to an initiatorline 192 which is unwound from a reel 104.

[0054] As depicted in FIGS. 2a and 2 b, the apparatus 10 is attached toa jumbo 34 with the loading head 12 attached by mounting bracket 68 torail 38 of the drilling system 36. The stemming kettle 92 and reel 88are mounted to the rear of the jumbo 34. The breach 98 is located in aposition where an operator of the jumbo 34 can easily manually load thecartridges 16 into the breach 98. The tube 14 has a relatively shortrigid section 106 which is supported by the cradle 74 and a flexiblehose portion 108 attached to an upstream end of the rigid section 106.The breach 98 is provided in the hose portion 108.

[0055] The operation of the apparatus 10 will now be described withparticular reference to FIGS. 3-11.

[0056] Referring to FIG. 3, the jumbo 34 (not shown in this Figure) isoperated in a conventional manner to drill the hole 20 into the body ofrock 24. As is known in the art, during this process, the drifter 40 isadvanced along the rail 38 to advance the drilling steel 42 into thebody of rock 24 producing a hole 20. While this is happening, theloading head 12, which is coupled to the rail 36 by the bracket 68, isdisposed so that the tube 14 is out of axial alignment with and lineallyspaced from, the face 22.

[0057] After the hole 20 has been drilled to a required depth, the jumbooperator operates the drilling system 36 so as to retract the drillingsteel 42 from the hole 20. This is achieved by sliding the drifter 40along the rail 38 away from the face 22 as shown in FIG. 4.

[0058] Next, as shown in FIG. 5, the motor 60 is operated to rotate theswing arm 44 (and thus the tube 14) about axis A, so that the tube 14 isin axial alignment with the hole 20. At this stage, the tube 14 remainsspaced from the face 22.

[0059] The extension cylinder 78 is now operated to extend the rod 76thereby sliding the carriage 70 along the member 52 and lineallyadvancing the tube 14 to the collar 18 of the hole 20, as shown in FIG.6.

[0060] Thereafter, a cartridge 16, to which an initiator lead 102 hasbeen attached, is inserted into the breach 98. The breach is thenclosed. The breach 98 when closed is provided with an opening to allowthe lead 102 to feed into the hose portion 108. Next, the reel 88 isoperated to pay out or advance the conduit 26 so that one end of theconduit 26 abuts the cartridge 16 and pushes it along the hose portion108 and rigid portion 106 of the tube 14 into the hole 20 and to the toe28 of the hole 20.

[0061] With the conduit 26 still in the hole 20, particulate stemmingmaterial 110 from the stemming kettle 92 is blown through the conduit26, and thus the tube 14, into the hole 20. The reel 88 is operated toretract or reel in the conduit 26 from the hole 20 as the stemmingmaterial flows through it. Accordingly, the hole 20 from the cartridge16 to the collar 18 is filled with particulate stemming material 110.The injection of stemming material ceases when the packed stemmingreaches the collar 18 of the hole 20. The extension cylinder 78 is againthen operated to retract the rod 76 sliding the carriage 72 along themember 52 away from the face 22 thus similarly lineally retracting thetube 14 from the face 22, as depicted in FIG. 8. The lead 102 is thencut. The motor 60 is operated to rotate the swing arm 44 about axis A torotate or swing the tube 14 out of axial alignment with the hole 20, asdepicted in FIG. 9. This action will cause at least a part of the lengthof the lead 102 to pull out of the tube 14. If any portion of the lead102 remains within the tube 14 it can easily be pulled out manually sothat it is free of the apparatus 10. The boom 32 of the jumbo is thenretracted to further space the apparatus 10 from the face 22, as shownin FIG. 10.

[0062] Finally, the lead 102 is attached to a battery or other type ofenergy source which is then operated to cause initiation of theenergetic material within the cartridge 16. This results in a fracturingof the rock in the vicinity of the hole 20 as schematically illustratedin FIG. 11. In particular, if the energetic material is a propellant itsinitiation can result in a penetrating core fracture of the rock. Thefractured rock if not released from the face 22 can be removed by animpact breaker.

[0063] The above process can then be repeated as required to causefurther fracturing of the rock 24.

[0064] Now that an embodiment of the present invention has beendescribed in detail it would be apparent to those skilled in therelevant arts that numerous modifications and variations may be madewithout departing from the basic inventive concepts. For example, in theillustrated embodiment, the cartridge 16 is attached to an initiatorlead 102 which is physically coupled to a battery or some other sourcefor providing power to initiate the energetic substance held within thecartridge 16. However in a further embodiment, the cartridge 16 may bedetonated by radio waves in which case the initiator lead 102 is notrequired. However in such an embodiment the cartridge 16 may (though notnecessarily) be provided with a short antenna for receiving the radiosignals. More particularly, the apparatus 10 may further include astemming bar coupled to a second swing arm and second carriage 70 whichcan be rotated into axial alignment with the hole 20 and then lineallyadvanced to bear on or support the particulate stemming material 110 inthe hole 20 where the stemming bar includes some form of transmitter fortransmitting a radio signal into the hole to provide either initiationsignals/commands which can be received by a circuit in the cartridge 16to initiate the energetic material. Indeed, the stemming bar and aninitiator in the cartridge can be configured in a manner as set out inApplicant's Patent Application No. PCT/AU98/00929 (the contents of whichis incorporated herein by way of reference) so that a signal istransmitted via that stemming bar also provide operational power for theinitiator.

[0065] In a further variation, rather than rotating the tube 14 (and/orstemming bar if provided) into and out of axial alignment with the hole20, the tube 14 (and stemming bar) can be moved lineally along an axisperpendicular to the axis B of the hole 20 into and out of axialalignment with the hole 20.

[0066] All such modifications and variations together with others thatwould be obvious to a person of ordinary skill in the art are deemed tobe within the scope of the present invention the nature of which is tobe determined from the above description and appended claims.

The claims defining the invention are as follows:
 1. An apparatus forfracturing a hard material, said apparatus including at least: a loadinghead provided with a guide for receiving a cartridge containing a chargeof energetic material, and guiding said cartridge into a hole formed ina face of a hard material to be fractured; a system for advancing saidcartridge along said guide to a toe of said hole; and, a stemming loaderfor loading a particulate stemming material into said hole through saidguide.
 2. The apparatus according to claim 1 wherein said system foradvancing said cartridge includes a flexible elongated member having afirst end which abuts an end of said cartridge distant said hole, and adevice for advancing and retracting said flexible elongated member. 3.The apparatus according to claim 2 wherein said flexible elongatedmember is a conduit and constitutes a part of said stemming loader, saidstemming loader further including a stemming injector for injectingparticulate stemming material into a second end of said conduit.
 4. Theapparatus according to claim 3 wherein said stemming injector includes ablower for blowing said particulate stemming material into and alongsaid conduit.
 5. The apparatus according to claim 1 further including analignment mechanism for moving said guide into and out of alignment withsaid hole.
 6. The apparatus according to claim 5 wherein said alignmentmechanism rotates said loading head about an axis parallel to an axis ofsaid hole, to move the guide into and out of alignment with said hole.7. The apparatus according to claim 5 wherein said alignment mechanismslides said loading head along an axis perpendicular to an axis of saidhole, to move the guide into and out of alignment with said hole.
 8. Theapparatus according to claim 5 further including a drilling system fordrilling said hole, said drilling system including a rail and a drillslidably mounted on said rail, wherein said alignment mechanism issupported on said rail.
 9. The apparatus according to claim 1 whereinsaid loading head includes a stemming bar which can be moved into andout of alignment of said hole for insertion into said hole to supportsaid particulate stemming.
 10. The apparatus according to claim 9wherein said stemming bar includes a transmitter for transmitting asignal into said hole for operating an initiator or a detonatorcontained in said cartridge.
 11. A method of fracturing a hard material,said method including the steps of: providing a guide for receiving acartridge containing a charge of energetic material; aligning said guidewith a hole formed in a face of a hard material; inserting the cartridgeinto said guide; advancing said cartridge along said guide into saidhole; injecting particulate stemming material through said guide intosaid hole; and, initiating said energetic material.
 12. The methodaccording to claim 11 including the step of advancing said guide intoabutment with said face of said hard material.
 13. The method accordingto claim 11 wherein said step of advancing said cartridge includespushing said cartridge along said guide.
 14. The method according toclaim 13 wherein said step of pushing includes advancing a length of aflexible elongated member into said guide to push said cartridge alongsaid guide into said hole.
 15. The method according to claim 14 whereinsaid step of injecting particulate material includes forming saidflexible elongated member as a conduit and blowing said particulatestemming material through said conduit into said hole.
 16. The methodaccording to claim 15 including a step of retracting said conduit fromsaid hole as said particulate material is blown into said hole.
 17. Themethod according to claim 11 including a step of attaching said guide toa drilling system which includes a rail and a drill mounted on said railand supporting said guide on said rail.
 18. The method according toclaim 11 including the step of providing an alignment mechanism formoving said guide into and out of alignment with said hole.
 19. Themethod according to claim 18 including a step of providing a stemmingbar coupled to said alignment mechanism, moving said guide out ofalignment with said hole; and moving said stemming bar into alignmentwith said hole and into abutment with said particulate stemming in saidhole.